Skip to content
 

That study about the health risks of red meat: An excellent news report

A couple different people pointed me to this excellent news article by Gina Kolata (with Brad Plumer), who writes:

Public health officials for years have urged Americans to limit consumption of red meat and processed meats because of concerns that these foods are linked to heart disease, cancer and other ills.

But on Monday, in a remarkable turnabout, an international collaboration of researchers produced a series of analyses concluding that the advice, a bedrock of almost all dietary guidelines, is not backed by good scientific evidence.

The distinction between truth and evidence. Check.

Kolata continues:

If there are health benefits from eating less beef and pork, they are small, the researchers concluded. Indeed, the advantages are so faint that they can be discerned only when looking at large populations, the scientists said, and are not sufficient to tell individuals to change their meat-eating habits.

The distinction between inference and decision. Check.

I don’t like this quote so much:

“The certainty of evidence for these risk reductions was low to very low,” said Bradley Johnston, an epidemiologist at Dalhousie University in Canada and leader of the group publishing the new research in the Annals of Internal Medicine.

Asking for certainty is typically a mistake.

Kolata then puts this into perspective:

The prospect of a renewed appetite for red meat also runs counter to two other important trends: a growing awareness of the environmental degradation caused by livestock production, and longstanding concern about the welfare of animals employed in industrial farming.

Then comes a clear distinction between aggregate and individual effects:

In each study, the scientists concluded that the links between eating red meat and disease and death were small, and the quality of the evidence was low to very low.

That is not to say that those links don’t exist. But they are mostly in studies that observe groups of people, a weak form of evidence. Even then, the health effects of red meat consumption are detectable only in the largest groups, the team concluded, and an individual cannot conclude that he or she will be better off not eating red meat.

And an expert quote reinforcing a key point:

David Allison, dean of the Indiana University School of Public Health—Bloomington, cited “a difference between a decision to act and making a scientific conclusion.”

It is one thing for an individual to believe eating less red meat and processed meat will improve health. But he said, “if you want to say the evidence shows that eating red meat or processed meats has these effects, that’s more objective,” adding “the evidence does not support it.”

Along with a relevant note:

Dr. Allison has received research funding from the National Cattlemen’s Beef Association, a lobbying group for meat producers.

And another perspective:

Evidence of red meat’s hazards still persuaded the American Cancer Society, said Marjorie McCullough, a senior scientific director of the group.

“It is important to recognize that this group reviewed the evidence and found the same risk from red and processed meat as have other experts,” she said in a statement. “So they’re not saying meat is less risky; they’re saying the risk that everyone agrees on is acceptable for individuals.”

Also some discussion of confounding:

“Do individuals who habitually consume burgers for lunch typically also consume fries and a Coke, rather than yogurt or a salad and a piece of fruit?” asked Alice Lichtenstein, a nutritionist at Tufts University. “I don’t think an evidence-based position can be taken unless we know and adjust for the replacement food.”

But this argument goes both ways. On one hand, sure, in an observational study it’s hard to untangle the difference components of diet and say that one particular food is bad for you. On the other hand, these observational data represent the real world, in which people don’t always eat “red meat” in isolation; rather, they’re eating burgers, fries, and a Coke, so we care about the effect of that too.

Some general concerns:

“I would not run any more observational studies,” said Dr. John Ioannidis, a Stanford professor who studies health research and policy. “We have had enough of them. It is extremely unlikely that we are missing a large signal,” referring to a large effect of any particular dietary change on health.

But, then again, the necessity of making decisions:

Despite flaws in the evidence, health officials still must give advice and offer guidelines, said Dr. Meir Stampfer . . . of the Harvard T.H. Chan School of Public Health. He believes that the data in favor of eating less meat, although imperfect, indicate there are likely to be health benefits.

One way to give advice would be to say “reduce your red meat intake,” Dr. Stampfer said. But then, “People would say, ‘Well, what does that mean?’”

Officials making recommendations feel they have to suggest a number of servings. Yet when they do, “that gives it an aura of having greater accuracy than exists,” he added.

And the conclusion:

Perhaps there is no way to make policies that can be conveyed to the public and simultaneously communicate the breadth of scientific evidence concerning diet.

Or maybe, said Dr. Bier, policymakers should try something more straightforward: “When you don’t have the highest-quality evidence, the correct conclusion is ‘maybe.’”

A fine ending, but we still need to decide what to serve for dinner! I’m left with no clear advice, but I applaud Kolata and Plumer for bringing up so many of the key statistical issues without getting distracted by non-issues such as statistical significance etc. There will undoubtedly be lots more reporting on this and related diet stories, and I hope that future news articles will continue this perspective.

In contrast, I’m less happy with this NPR report by Alison Aubrey, which to my taste puts too much of the focus on a narrow statistical issue of how particular studies are rated and doesn’t get to the larger concerns of aggregate vs. individual effects, truth vs. evidence, and the necessity of decision making. But my point here is not to slam this NPR report; it’s the way that such scientific controversies are typically covered in the news. The above-linked NYT article points to a better way forward.

42 Comments

  1. yyw says:

    NPR report didn’t seem that bad. I don’t expect much out of journalists when it comes to science reporting anyway. The statements of scientists quotes on the other hand are truly worrying. “outraged and bewildered”, “clear evidence for harm associated with high red meat intake”, and the claim that “there is a consensus already.”

    Also this quote from Washington Post article, “The biggest cost [to studies like these] is, people will throw up their hands and say nutritional science doesn’t know what it’s talking about.”

  2. Terry says:

    I have been reading articles pointing out the woeful lack of evidence against red meat for about thirty years now. The counter arguments seemed pretty good thirty years ago and have only gotten stronger since then. About twenty years ago, I thought the link had been pretty much totally debunked (leaving room for perhaps a very weak link).

    Why has this process taken so long?

    • Malcolm Kass says:

      Yes, I agree. I heard about these problems years ago.

    • Eric says:

      Once you dig deep enough, you will discover there is a very active underground, agenda driven campaign, by vegan/vegetarian types, who actively push their cherry picked science into the media. It’s incredibly widespread, people just are not aware because they have not researched this in depth.

      They have been very successful at this. The mean industry has utterly failed to push “their side of the science”. Both sides are biased, but one is clearly winning.

      This is finally starting to turn around, because they science simply does not support the side being pushed the most.

      Plant based diets have kept me very ill for decades, so thats my bias. I cured all my autoimmune diseases by going on a near all meat diet and dropping all vegetables. Fruit is OK.

      The “plant based diet” push, but these groups, have effectively kept me from being 100% healthy for two decades.

      I suggest joining all the carnivore groups and facebook. Not because I promote this diet, but to watch all the fascinating anecdotal stories flying by every day. Its quite stunning.

  3. jim says:

    Glad to see you bring this up! This night be the first time actual science has been applied to the question. I eagerly await annoneuoids comments😁

  4. Joshua Pritikin says:

    There’s only one diet proven to reverse heart disease: a whole food plant-based. This diet can also reverse Type 2 diabetes. See “Prevent and Reverse Heart Disease” by Caldwell B. Esselstyn.

    > Also this quote from Washington Post article, “The biggest cost [to studies like these] is, people will throw up their hands and say nutritional science doesn’t know what it’s talking about.”

    Well, yeah. That’s is my concern too. Watch https://gamechangersmovie.com/

    • Jonjo Shelvey says:

      It is much better for nutritional science in the long term to be hones about the shortcomings of their research. The ever conflicting statements made about food from decade to decade(usually based on weak or flawed studies which do not generalize on the population as a whole) are the source of disbelief among the public towards nutritional science. Hence, the field should acknowledge the shortcomings of their current knowledgeprescriptivism

      • Joshua Pritikin says:

        I am all for acknowledging the shortcomings in research. I am also all for pointing out meat and dairy industry conflicts of interests and tobacco style science strategy, https://nutritionfacts.org/video/big-food-using-the-tobacco-industry-playbook/

      • yyw says:

        Exactly, you don’t need to look at anything else but the constantly changing nutritional guidelines to be skeptical about nutritional science. If evidence is weak, be honest about it. Only put items with strong evidence and large effect in a guideline. Even then, emphasize uncertainty and ways that science could get it wrong.

        Lack of knowledge by itself in a discipline doesn’t generate mistrust. It is the lack of knowledge combined with a lack of either humility or honesty or both.

      • Aryeh says:

        Jonjo Shelvey: “It is much better for nutritional science in the long term to be hones about the shortcomings of their research.”

        … but that would destroy the prestige and incomes of the “Nutritionist Profession”.

        Nutrition Experts enjoy high status in American society… and they are everywhere in the medical establishment, government, schools, food industry and media.
        Their phony mystique as objective scientists/analysts is the entire basis of their influence.

        Would you expect psychologists and economists to ever generally “be honest about the shortcomings” of their abundant speculative professings?

      • eric says:

        This is sheer nonsense and blatant vegan propaganda.

        Studies like the tiny tiny Ornish diet study confounded tons of lifestyle changes, including quitting smoking, with an ultra low fat diet, and then attempts to give credit to low fat, and the cause of the alleged heart disease reversal. Pure bunk. Dunked many times. Worst science full of confounding variables. Never repeated.

  5. Imaging guy says:

    Probably the first published study in nutritional science

    “The first published report of a clinical trial has biblical origins. In the Book of Daniel,5 reference is made to the unwillingness of the Israelite Daniel to accept the diet offered by the Babylonian king Nebuchadnezzar. The king’s official had put a steward in charge of Daniel and his three friends (Shadrach, Meshach, and Abednego):

    Daniel said to the steward . . . “Test your servants for ten days; let us be given vegetables to eat and water to drink. Then let our appearance and the appearance of the youths who eat the king’s rich food be observed by you, and according to what you see deal with your servants.” So he hearkened to them in this matter, and tested them for ten days. At the end of ten days it was seen that they were better in appearance and fatter in flesh than all the youths who ate the king’s rich food. So the steward took away their rich food and the wine they were to drink and gave them vegetables.”
    https://www.nejm.org/doi/full/10.1056/NEJM200301023480120

  6. Alex C. says:

    And in similar news:

    Researchers: “Antidepressants Should Not be Used for Adults with Major Depressive Disorder”
    In a new article, researchers directly state that antidepressants should not be used since there is insufficient evidence of benefit and evidence for the risk of potential harms. They base this conclusion on a thorough review of the existing studies.

    “The benefits of antidepressants seem to be minimal and possibly without any importance to the average patient with major depressive disorder,” they write. “Antidepressants should not be used for adults with major depressive disorder before valid evidence has shown that the potential beneficial effects outweigh the harmful effects.”

  7. Jonathan (another one) says:

    We’ve seen this before, of course. The removal of dietary cholesterol limits for lack of evidence relating to cardiovascular disease took years, with the same sorts of “outrage” from nutritionists whose self-worth seemed to revolve around hectoring people. No amount of data that showed that lowering of dietary cholesterol had minimal (if any) effects on cardiovascular disease mattered. Indeed, until statins were in widespread use to lower blood cholesterol directly (and had an easily measurable effect on CVD rates) did the anti-dietary cholesterol zealots yield on the recommendations sufficiently to allow people to eat eggs again.

  8. Joshua Pritikin says:

    Study Selection Criteria:

    + “Randomized trials (published in any language) comparing diets lower in red meat with diets higher in red meat that differed by a gradient of at least 1 serving per week for 6 months or more.” https://annals.org/aim/fullarticle/2752326/effect-lower-versus-higher-red-meat-intake-cardiometabolic-cancer-outcomes

    + “Cohort studies that included more than 1000 adults and reported the association between consumption of unprocessed red and processed meat and cancer mortality and incidence. https://annals.org/aim/fullarticle/2752321/reduction-red-processed-meat-intake-cancer-mortality-incidence-systematic-review

    + “Cohort studies with at least 1000 participants that reported an association between unprocessed red or processed meat intake and outcomes of interest.” https://annals.org/aim/fullarticle/2752320/red-processed-meat-consumption-risk-all-cause-mortality-cardiometabolic-outcomes

    Given these selection criteria, I’m not surprised by the conclusions. I agree there is probably no difference between red meat and other types of meat. However, these studies basically say nothing about the comparison that I care about: whether to eat or abstain from eating any type of animal product.

    • Jonathan (another one) says:

      Maybe not what you’re interested in, but certainly squarely in line with, for examine, what the Heart Association recommends: https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/meat-poultry-and-fish-picking-healthy-proteins
      “It’s OK to eat meat as long as you limit the amount and choose healthier types.”
      “Minimize processed red meats like bacon, ham, salami, sausages, hot dogs, beef jerky and deli slices.”
      “AHA Recommendation: Choose nonfried fish, shellfish, poultry without the skin, and trimmed lean meats, no more than 5.5 ounces, cooked, per day.”

    • Martha (Smith) says:

      Joshua said,
      “However, these studies basically say nothing about the comparison that I care about: whether to eat or abstain from eating any type of animal product.”

      And such a decision might involve other factors besides whether or not they are healthy for the person consuming them — in particular, more and more people are becoming concerned about the effects of consuming animal products on global warming — see, for example the “Grandparents’ Diet” (https://www.nutritionaction.com/daily/what-to-eat/the-grandparents-diet/)

    • jim says:

      “these studies basically say nothing about the comparison that I care about”

      I think that’s exactly the point. You can find something that “says” something about whether eating meat is healthy or not. It’s just not science.

      • Joshua Pritikin says:

        I respectfully disagree. “Prevent and Reverse Heart Disease” by Caldwell B. Esselstyn is science.

        • Jonathan (another one) says:

          Uncontrolled studies are emphatically not science. From https://sciencebasedmedicine.org/bill-clintons-diet/

          “It works. In the first continuous twelve-year study of the effects of nutrition in severely ill patients, which I will describe in this book, those who complied with my program achieved total arrest of clinical progression and significant selective reversal of coronary artery disease.”

          That’s misleading. He was not studying diet alone; his patients were also taking cholesterol-lowering medication. With no control group, how do we know the results were due to the diet rather than to other factors, like the intensive counseling or the medications they were taking? Statin therapy alone has been shown to cause regression of coronary lesions. I would like to see controlled studies comparing statins to diet to a combination of both, or comparing Esselstyn’s strict diet to another, less strict, diet that controls calories, ensures good nutrition, and produces weight loss.

          • Andrew says:

            Jonathan:

            To say uncontrolled studies are not science is too strong. An uncontrolled study can be science. Imperfect science, sure, but it can still be science. A simple before-after study can be science.

          • Anoneuoid says:

            Uncontrolled studies are emphatically not science.

            Astronomers have no control group and have been far more successful at predicting the future than the fields where they use control groups all the time. It is almost as if comparing treatment to control over and over isn’t such a useful method for learning about the world.

            • Navigator says:

              Well,

              Astronomy is dealing with fairly established laws of Physics that allow for stable predictions. Try doing that in Social Psych., Economics, etc. All you really need in many basic experiments in Physics are the descriptive statistics. Counting, comparing and reporting. The laws of Physics do the job for you. Not so much in other ‘noisier’ fields.

              The further a given field is from pure Physics, the more noise, extraneous variables, cause-effect relationships become a big issue.

              I hate to say this, but the experiments in Physics are far simpler than in, say, Cognitive Psychology. The rigor and careful measurement is more precise, but once you’ve collected the date, the rest is fairly simple. Of course, this doesn’t apply to some uncharted parts of Physics where uncertainty abounds.

              Thanks

              • Anoneuoid says:

                Astronomy is dealing with fairly established laws of Physics that allow for stable predictions. Try doing that in Social Psych., Economics, etc.

                Correct.

                A) In astronomy they looked for universalities and discovered laws of nature that allow accurate predictions of the future.

                B) In those other fields they look for differences between groups and did not discover any laws of nature and they cannot make good predictions about the future.

                The lesson is to do the thing the astronomers did, and not do the thing the social science researchers did. If you applied the social science approach to physics you would make just as much progress on that subject matter as elsewhere.

  9. Peter says:

    Interesting response to the new paper reported on by Gina Kolata in the New York Times, from Harvard University:
    https://www.hsph.harvard.edu/nutritionsource/2019/09/30/flawed-guidelines-red-processed-meat/

    Some comments:
    “the advantages [of reducing meat consumption] are so faint that they can be discerned only when looking at large populations, the scientists said, and are not sufficient to tell individuals to change their meat-eating habits.” (Kolata)
    On what basis can scientists say that the advantages are not sufficient to tell individuals to change their meat-eating habits?

    So the gist of this new research report is:
    a) negative health effects of eating a lot of meat are small (which is not news) and
    b) the effect estimates come from observational studies (also not news), which these researchers deem ipso facto as only able to generate weakly persuasive evidence

    Note also that the effectiveness (for reducing mortality) of asymptomatic screening for breast cancer and colon cancer are weak. However, in the US billions of dollars are spend each year on these types of screening. In a March 2011 article in the journal Significance (journal of the Royal Statistical Society), entitled How Should We Screen for Breast Cancer, Howard Wainer wrote that a conservative estimate of the annual costs of mammograms is $5.5 billion.

    In both cases, asymptomatic screening and meat consumption, effect sizes are reported as relative risk reductions. Paging Gerd Gigerenzer!:
    https://journals.sagepub.com/doi/full/10.1111/j.1539-6053.2008.00033.x

    What is true is that:
    – moderate or even large relative risk reductions often are equivalent to small absolute risk reductions
    – experts who make population-level recommendations often think in terms of how small absolute risk reductions applied to a large population yield significant number of premature deaths prevented

    Personally, I think that ignoring the environmental impacts of meat consumption is bad.

    Also, the animals killed for meat, dairy, egg and fish consumption are sentient beings; that is, they can feel pleasure and pain. Why is it acceptable to impose pain on them, just because meat eaters like the taste of meat?
    Primo Levi wrote the following in his essay Against Pain (reprinted in Other People’s Trades, New York, 1989):
    “Animals must indeed be respected … Not because they are ‘good’ or useful to us (not all of them are), but because a rule written in us and recognized by all religions and all legislations commands us not to create pain, neither in ourselves nor in any creature capable of perceiving it … the certitudes of the layman are few, but the first is this: suffering (and inflicting suffering) is acceptable only if rewarded by the avoidance of greater suffering to oneself or others.”

    Also interesting, article by Aaron Carroll in the New York Times:
    Meat’s Bad for You! No, It’s Not! How Experts See Different Things in the Data. Oct.1, 2019
    https://www.nytimes.com/2019/10/01/upshot/health-risks-meat-experts.html

  10. Navigator says:

    Gretings!

    The fact that nutrition studies are not well designed and lack experimental rigor (control, randomization, intervention, cross-over, etc. double/triple -blind) and the apparent lack of the harmful effects of meat, does not mean meat is good for us either.

    The article states: “The evidence is too weak to justify telling individuals to eat less beef and pork, according to new research.”

    Well, how did ‘telling the individuals’ go? Just like the food pyramid, it was a suggestion by ADA, and we all know how well people listen to those types of advice.

    So, if the advice to avoid meat was incorrect due to insufficient evidence, but people kept eating meat, where did heart disease come from?

    I believe same is happening with the food pyramid. All of a sudden the grains are the culprit, as if anyone listened to ADA’s suggestions. People were stuffing their faces with everything, mostly fat and meat during the ‘reign’ of now-hated food pyramid. The sales of barbecue gadgets didn’t go down during the ‘pyramid times’, but let’s blame oatmeal and corn flakes.

    All these ‘debunking’ studies reveal is that properly designed research studies are sorely needed, but we already know that.

    Thanks

Leave a Reply